No you don't ever have to move in an arc. Standard movement forces you into it in some situations, but it is by no means necessary in any case. I'll say it again, just move in a straight line to where you need to be. That's it. I also never once said you only have to stay at the transition to be able to do positionals. If you think I did then you need a lesson in reading comprehension.
Straight line implies that the boss is only moving on the X axis when that's clearly not the case; in many situations the boss does aoes that cover its entire body as well. What you both seem to not understand is that I'm not talking about striking dummies, I'm talking about bosses that continually have mechanics and aoes; and not all are the same size either. But of course, these factors are foreign to you.

I'm ignoring your bad attempts at humble bragging about the skill needed to use legacy because it's just a humble brag and either Legacy is easier or harder, not both.
The irony, you talk to me about reading comprehension and nowhere did I say that legacy movement is harder than standard. What I stated is that for some jobs, specially melee, standard movement seems to be more appropriate, in my experience. I never said it was hard using it on melee; but like I said, I'm completely not surprised.